i do have a shell script doing :

`man "#{arg}" 2> "#{tmp}/#{fm}" PIPE man2html > "#{tmp}/#{f1}"`

because i want to know if there is "No manual entry for "#{arg}""

then for the time being i'm using an tmp file "#{tmp}/#{fm}"  which i
read after to know i i get the message :

"No manual entry for "#{arg}""

i'm sure there is a more elegant way doing that in Ruby, avoiding
shelling, BUT HOW TO ?